Process for the recovery of paste from printed paper, and chiefly wood paste



Patented; Feb. 3, 1931 I UNITED STATES PATENT oFFic-E' LOUIS GBENAUDIEB, OF PARIS, FRANCE PROCESS FOR THE RECOVERY OF PASTE FBOlW. PRINTED PAPER, AND GHIEFL? WOOD PASTE 4 No brewing. Application filed October 13, 1927, Serial No. 227,865, and in France October 25, 1926.

I The present invention relates to a process for the recovery of paste from printed paper and chiefly wood paste.

In view of the constantly increasing con- 5 sumption of paper used for the printin of journals, which leads to a diminution o the forestry capital in countries producing wood paste, attempts have been made during the past period to effect the recovery of cellu- 1o lose from old newspapers. v

None of the processes within my knowledge have proved successful, and this for the same reason, i. e. ink is generally removed by the action of an alkaline solution, and the ink is dissolved .in this solution, so that the fibres assume a uniform gray color, and to remove this color'the substance must be frequently washed, this being expensive, or it must be treated with bleaching agents where-- so by it is altered to a greater or less degree.

The process according to my invention will remove the ink and at the same time separate the ink from the fibres in a spontaneous and approved manner. In my said process, I

form by means of the fatty parts of the ink, an insoluble scum or foam which takes up andvwithdraws the color, so that the alkaline bath will remain quite clear. Subsequent washing is unnecessary, and the hot water used to remove the ink may be recovered for another operation. It is simply necessary to analyze it once for all, in order to find the amount of chemical products to be added in order to make it available for as further use.

My said process is applicable to all classes of wood paper, and can also be used for the removal of ink from; all varieties of printed paper. The cellulose thus recovered can be 40 used for most of the purposes for which new .cellulose is employed.

My said process comprises two essential stages, as follows:

1.-The old newspapers (or like printed paper) are softened by immersion for several hours in ordinary water, and are then defibrated as completely as possible. If the breakers in current use in paper making are employed, and these appear to benwell adapted for the purpose, care must be taken to separate the roller from the plate. In this manner the paper is not defibrated by trituration between the spikes of the roller and the plate but by the effect of water, by a beating action. This method has two.ad

vantages; it obviates the shortening of the I add to the defibrating water a certain.

quantity of soluble soap, i. e, an alkaline soap for instance 1 part in 2000. The color is taken up by the fatty substance and there is formed a black foam or scum on the surface of the liquid.

2.When the defibrating process is completed,'the resulting paste is disposed'in a tank which, is heated by direct fire or b steam. The said tank contains a very wea solution of an alkaline salt. I prefer to use sodium carbonate of about 1 to 1500 strength; the proportion should never exceed 1 in 800, or the fibres would be attacked and yellowed. I use a suflicient amount of this solution to form a light broth with the paste. If the material is heated over an open fire, care must be taken to avoid concentrating the bath by evaporation, this can be avoided by the addition of water from time to time during the operation. At the beginning of the ebullition, an abundant and ver black foam is formed on the surface; tlllS ceases to be produced after a rather short time, which varies with the amount of paper under treatment. I may find by experiment the duration of the treatment for any given quantities.

The said foam or scum is then eliminated either by skimming, by suction, by overflow discharge, or by like means. The said scum contains paper fibres,-a-nd it can thus be dried and compressed in order to form gray pasteboard (tarboard). Obviously, I-may recover the fatty substance, and even the coloring matter contained in the said foam or scum.

The paper paste will rapidly collect upon the bottom of the tank, and it can be suitably collected. The hot water can also be recovered.

To further'the formation of the foam or scum, I may provide the tank with suitable oil in the ink is saponified, and this forms a soluble salt which tends to be taken up by the alkaline bath.

2. However, if care has been taken to use water which is sufficiently calcareous, the soap which continues to be formed Will'be made insoluble.

This explains the formation of a foam or scum which contains the coloring matter of the ink which has been removed from the fibres during the first period of the operation.

The preceding considerations show that it is an essential feature to employ a natural water which is sufliciently calcareous, for instance the water of certain rivers. But if the available water is not sufficiently calcareous, such substances may be added, or the process may be variously employed according to the following conditions.

1.I may add to the ink removing alkaline solution a metallic salt which renders the soap insoluble.

2.I may add to the said solution a salt of an alkali metal, adapted for separating purposes such as common salt. The water will no longer dimolve the soap, andthis latfor will collect on the surface. 7

3.The soap which is formed may be decomposed by the use of an acid whereby the fatty acids of the soap will be set free, and due to their small density, the said acids will collect on the surface.

In certain cases, it may be advantageous to add to the ink removing solution, a solvent for the ink, or substances capable of changmg the capillary action of the said solution, thus furthering the formation of the said scum; for instance, albumen, casein, gelatin, glucose, or the like, or substances changing the ittgture of the fibres, such as bleaching agen What I claim is:

1. In a process for the recovery of paste I from printed paper, and chiefly from wood paste, which process consists in treating the paste with an alkaline lye bath to form an alkahne soap with the fatty matter of the mk the use of a. suitable substance for rendering insoluble the said soap whereby said ink containing soap rises to the top of the bath and does not mix with the paste in the bottom of the bath.

2. In a prooes for the recovery of paste from pmnted paper, and chiefly from wood paste, which process comprises treating the paste with an alkaline lye bath to form an alkaline soap with the fatty matter of the ink, and adding an acid to said bath whereby the fatty acids of the soap will be set free and said inkcontaining soap will rise to the top of the bath and does not mix with the paste in the bottom of the bath.

3. -A process for the recovery of the paste of printed paper, and chiefly of wood paste, which process consists in effecting a preliminary removal of the fiber from the paper, in treating the paste from which the fibers have been thus removed with a bath of sodium carbonate of approximately 0.001 strength, operating at the boiling point, thus forming a soda soap with the fatty substances of the ink, and in the systematic addition to thetreating bath of a substance by which the resulting soap will be made insoluble as fast as formed.

4. In the method of removing ink from paper, the steps of treating the paper in an alkaline bath having an alkalinity not exceeding that of a solution of 1 part of sodium carbonate in 1000 parts of water, whereby a soap will be formed, and adding a substance to the bath which will render said soap insoluble, whereby said ink containing soap rises to the top of the bath and does not mix with the paste in the bottom of the bath.

5. In the method of deinking paper, the

steps of treating the paper in an alkaline bath having an alkalinity not exceeding that of a solution containing 1 part of sodium carbonate in 1000 parts of water, and adding an acid to said bath, whereby any soap formed may be rendered insoluble and said ink containing soap rises to the top of the bath and does not mix with the paste in the bottom of the bath.

In testimony whereof I have signed this specification.

LOUIS GRENAUDIER. 

